1. Field of the Invention
The present invention relates to an optical disc, and more particularly, to a method of recording physical address information on an optical disc and an optical disc having physical address information.
2. Description of the Related Art
Generally, when recording data on an optical disc, a basic recording unit having a fixed size is used throughout the optical disc and is referred to as a recording block or an error correction code (ECC) block. When a single recording block is recorded on the optical disc, a recording physical address indicating a position of the recording block on the optical disc is also recorded. All physical recording addresses are recorded throughout the optical disc and have the same size and structure.
A conventional method of recording address information indicating an address of a recording block on an optical disc may include generating a wobble signal by performing wobble modulation on the address information and making a track of the optical disc have the same shape as the wobble signal.
FIG. 1 illustrates a disc track having the same shape as a wobble signal indicating physical address information.
Wobble modulation methods include monotone wobble (MW) modulation, saw tooth wobble (STW) modulation, binary phase shift keying (BPSK) modulation, frequency shift keying (FSK) modulation, and minimum shift keying (MSK) modulation. Since wobble modulation on address information is advantageous for improving optical disc access characteristics such as motor speed control, the method is widely used for recording address information of a recording block on an optical disc.
In addition to the address information, other kinds of information, such as a type and properties of the optical disc, may be included in a wobble. Throughout the optical disc, only a single type of wobble is used and recording addresses have the same structure when the recording address information is included in the wobble.
Referring to FIG. 1, the track has the same shape as a wobble signal generated according to MW modulation in which the address information is modulated into single-frequency sine waves. A mark corresponding to recording data is formed in the middle of the track. As shown in FIG. 1, the wobble signal shaped on the track and indicating an address of a single recording block has the same length as the single recording block.
FIG. 2 illustrates a wobble signal generated using a conventional phase-shift keying (PSK) modulation. The wobble signal shown in FIG. 2 corresponds to 10 periods of a basic wobble signal. In FIG. 2, a curved line in an upper portion represents a wobble signal shaped on a track, and a square line in a lower portion represents square waves generated by processing the wobble signal, which has been read by a pickup of an optical disc drive, using a predetermined method.
The square waves shown in FIG. 2 indicate data values 0, 1, 0, 0, 0, 0, 1, 1, 0, and 0 included in the wobble signal corresponding to 10 periods of the basic wobble signal. A wobble signal corresponding to 83 periods of the basic wobble signal having a data value of “0” is recorded in front of the wobble signal corresponding to the 10 periods of the basic wobble signal. A wobble signal corresponding to the 93 periods of the basic wobble signal indicates a single address information bit value of “1”. A recording address of a single recording block is expressed using a total of 52 bits.
FIG. 3 illustrates a wobble signal generated using a conventional MSK modulation. The wobble signal corresponds to 8 periods of the basic wobble signal.
Wobbles corresponding to a single period of the basic wobble signal have different frequencies of “f” and “1.5f”. According to the conventional MSK modulation, a single address information bit is expressed by a wobble signal corresponding to 56 periods of the basic wobble signal. A value of the single address information bit is determined by a position of three consecutive wobbles sequentially having frequencies of 1.5f, f, and 1.5f, respectively, in the wobble signal corresponding to 56 periods of the basic wobble signal. According to the conventional MSK modulation illustrated in FIG. 3, a total of 83 bits express a recording address of a single recording block.
FIG. 4 illustrates an example of a conventional method of recording a physical address on an optical disc using a land-pre pit (LPP). When the optical disc includes a land track and a groove track, data such as user data is recorded on the groove track and pits indicating a corresponding physical address are formed on the land track.
Referring to FIG. 4, a data value is determined by the existence or non-existence of a pit at a peak of a monotone wobble formed along the land track. In other words, when a pit is formed on the land track, a data value is “1”. When a pit is not formed on the land track, a data value is “0”. When 208 such data values are obtained, 12 address information bits are expressed. 192 address information bits express an address of a single recording block.
Recently, an attempt has been made to use an optical disc as an information storage medium for a portable electronic apparatus, e.g., a camcorder, recording and/or reproducing audio information and video information together. However, it is problematic to use a conventional optical disc in a portable electronic apparatus. For example, a conventional optical disc having a size of 80 mm or 120 mm is too big to be used as an information storage medium for a camcorder and also requires a large amount of power.
To use an optical disc as an information storage medium for a portable electronic apparatus, such as a camcorder or a digital camera, a compact optical disc having a smaller size and a higher data recording density than the conventional optical disc is desired. However, when data is recorded on the compact optical disc using a conventional recording block (or ECC block), problems may occur in an inner radius area of the compact optical disc.
FIG. 5 illustrates an innermost circumference area of a compact optical disc on which data is recorded in units of conventional recording blocks. Referring to FIG. 5, when data is recorded in units of conventional 64-Kbyte recording blocks in a data recording area at the innermost circumference having a radius of 6 mm on the compact optical disc in a direction from an inner radius to an outer radius, a single conventional recording block occupies a region from point A to point D. In other words, the single conventional recording block occupies two tracks, having an overlap in a radial direction of the compact optical disc. When a defect occurs in the radial overlap of the recording block due to a scratch, dust, or a fingerprint, the defect is more severe than a defect occurring in a non-overlap portion of the recording block. As a result, error correction performance may be remarkably decreased, thereby deteriorating the reliability of the reproduced data.
To prevent a radial overlap from occurring in a recording block, different formats of recording blocks may be used. In detail, data is recorded in an inner circumference area on a compact optical disc in units of first recording blocks which are shorter than a predetermined track at an inner circumference of the compact optical disc, and is recorded in other areas on the compact optical disc in units of second recording blocks that are longer than the first recording blocks. The second recording blocks that are longer than the first recording blocks are used because bigger recording blocks are more advantageous in terms of error correction.
However, when different formats of recording blocks exist in a data recording area, an address of a recording block cannot be recorded on a compact optical disc. This is because, according to the conventional technology illustrated in FIG. 1, the length of the address information indicating an address of a single recording block is the same as the physical length of the recording block, and a single address recording method and a single address information system are used throughout the compact optical disc. Accordingly, a new address recording method is desired.
Meanwhile, a problem of a radial overlap in a recording block occurs in a smaller radius, e.g., of about 6 mm, than an inner radius of a conventional compact optical disc as well as in an inner circumference area of the conventional compact optical disc.